N-HALOALLYL-p-PHENYLENEDIAMINES

ABSTRACT

A para-phenylenediamine of the formula   WHEREIN R1, R2 and R3 are hydrogen or halogen, at least one being halogen, useful for the preservation of rubber.

llniied States Patent DAmico et al. 51 Mine 6, W72

54] N-HALOALLYL-P- 2,901,459 8/1959 Merrifield ..260/45.9

PHENYLENEDIAMINES 3,211,793 10/1965 R665 ..260/576X [72] Inventors: JohnJ. DAmlco, Akron; Sidney T.

Webster, Worthington, both of Ohio |"I;l| Armlgnec: Monsanto Company,81. Louiu, M0.

22 Filed: Mar. 20, 1970 21 Appl. No.: 21,542

52 us. c1. ..260/576, 260/459 R, 260/809 51 lm. c1 ..C07c 87/48 58 Field61 Search ..260/576 [56] References Cited UNITED STATES-PATENTS2,115,473 4/1938 Semon ..260/45.9 x

Primary Examiner-Joseph Rebold Assistant Examiner-C. F. WarrenAttorney-Richard O. Zerbe, .l. E. Maurer and Neal E. Willis [57]ABSTRACT A para-phenylenediamine of the formula 3 Claims, N0 Drawings 1N-HALOALLYL-P-PHENYLENEDIAMINES This invention relates top-phenylenediamines and their use as antidegradants. More particularlythis invention pertains to N-haloallyl-N'-phenyl-p-phenylenediamines.

BACKGROUND OF THE INVENTION N-Phenyl-para-phenylenediamines are usedextensively as antidegradants in the rubber industry. They areparticularly important in protecting rubber from attack from ozone,especially whenthe rubber article is flexed while in use. Many N-substituted N'-pheny1-p-phenylenediamines have been prepared and testedincluding N-a1kyl-, N-alkeny1-, N-aralkyl-, N-arylandN-alkaryl-N'-phenyl-p-phenylenediamines. TheN-alkyl-N-phenyl-p-phenylenediamines are used extensively because oftheir exceptionally high antiozonant activity, although they do reduceprocessing safety by activating cure.N-alkenyl-N'-phenyl-p-phenylenediamines are, in general, less effectiveantiozonants and similarly cure activating. An improved class ofN-alkenyl-N-phenyl-p-phenylenediamines has now been found.

SUMMARY oF THE INVENTION We have discovered that the presence of halogenon one or both carbons of the ethenically unsaturated bond ofN-alkenyl-N'-phenyl-p-phenylenediamine enhances antiozonant activity.The presence of a halogen atom on carbon of-the double bond results inenhanced antiozonant activity coupled with reduced affect on cure. Thus,there has been discovered a new and improved class ofN-alkenyl-N-phenyl-p-phenylenediamines ofthe formula wherein R R and Rare hydrogen or halogen, at least one being halogen. The halogen may beselected from the group consisting of chlorine, bromine, iodine orfluorine or'mixtures thereof. The mono-chloro compounds are preferred.

The N-hal oallyl-N'-phenyl-p-phenylenediamines may be prepared by thecondensation of a polyhalopropene with 4- aminodiphenylamine in thepresence of an acid acceptor.

Examples of suitable polyhalopropene reactants are 1.3- dichloropropene,I 2,3-dich1oropropene, 1,2,3- trichloropropene,1,1,2,3-tetrachloropropene and their bromo and iodo counterparts ormixed halopropenes, such as l-chloro-3-bromopropene,2-chloro-3-bromopropene, 1,2- dichloro-3-bromopropene,l,1,2-trichloro-3-bromopropene and the like.

lllustrative examples of the compounds of this invention are N (2chloroallyl) N phenyl p phenylenediamine. N (2-bromoallyl)-N'-phenyl-p-phenylenediamine, N-(2-iodoallyl)-N-phenyl-p-phenylenediamine,N-(2-fluoroallyl)-N'-phenylp-phenylenediamine, N-( 3-chloroallyl)-N'-phenyl-p-phenylenediamine, N-( 3-bromoallyl )-N'-phenyl-p-phenylenediamine, N 2,3-dichloroal1yl )-N'-phenyl-p-phenylenediamine,N-(2,3-diiodoallyl)-N'-phenyl-p-phenylenediamine,N-(3,3-dichloroallyl)-N'-phenyl-p-phenylenediamine,N-(3,3-difluoroallyl)-N'-phenyl-p-phenylenediamine, N-(2,3,3-trichloroa1lyl )-N'-phenyl-p-phen ylenediamine,N-(2,3,3-tribromoallyl)-N'-pheny1-p-phenylenediamine, N(3-bromo-2-chloroa1lyl )-N-pheny1-p-phenylenediamine, andN-(3-chloro-2-bromoallyl)-N-phenyl-pphenylenediamine.

The N-(haloallyl)-N'-phenyl-p-phenylenediamines protect rubber from thedegradation caused by the deleterious effects of ozone. Protection isobtained by incorporating an antiozonant amount of the material into therubber composition preferably before vulcanization and the protectioncontinues after vulcanization. The compounds effectively inhibit ozoneattack of sulfur vulcanizable rubbers such as natural rubber andsynthetic diene rubbers. The diene rubbers contain suffcientunsaturation that they can be vulcanized with sulfur or sulfurcontaining compounds. Synthetic diene rubbers which are protectedinclude polymers of 1,3-butadiene, of isoprene or mixtures of the twopolymers, copolymers of 1,3-butadienes with other monomers, for example,styrene, acrylonitrile, isobutylene or methyl methacrylate and polyolefmrubbers such as ethylenepropylene terpolymers (EPDM).

The amount of antiozonant used depends on a number of factors such astype of elastomer, end use of the vulcanized product and othercomponents in the formulation. The amount is usually between 0.1 to 5parts by weight per parts by weight rubber. Generally, the amount isbetween 0.5 to 2 parts by weight antiozonant.

DESCRlPT ION OF THE PREFERRED EMBODIMENTS N-( 2-Chloroallyl)-N'-phenyl-p-phenylenediamine is prepared as follows: To a stirredmixture of 184.2 g. (1.0 mole) of 4-aminodiphenylamine and 121.5 g. (1.2mole) of triethylamine at 85 C. is added 1 13.2 g. (1.02 mole) of 2,3-dichloropropene while the temperature is maintained between 80-90 C. Themixture is heated to 1 10 C. in 25 minutes and refluxed between -129 C.for 2.5 hours during which time salt formation is observed. The mixtureis cooled to 1 10 C. and 225 g. (1.4 mole) of 25 percent NaOH solutionis added after which 250 ml. of water is added to dissolve the saltwhich formed. The reaction mixture separates into two phases of whichthe organic phase is recovered and the water phase discarded. Lowboiling constituents are removed from the organic phase by heating invacuo up to 205 C. at 1.0-1.5 mm. Hg. The residue is distilled to give99.5 grams of N-(2- chloroallyl)N-phenyl-p-phenylenediamine, b.p.188-198 C. at 0.5 mm (mainly l94l95 C. at 0.5 mm.). Recrystallized fromheptane, the product is a white solid which melts at 5657.5 C. Analysisgives 10.48 percent N and 13.57 percent Cl compared to 10.83 percent Nand 13.70 percent CI calculated from C l-1, N Cl.

N-( 3-Chloroallyl )-N-phenyl-p-phenylenediamine is prepared by followingthe above procedure except 1,3- dichloropropene is used in place of2,3-dich1oropropene. N- 2,3-dichloroal1y1)- N'-phenyl-p-phenylenediamineis prepared in like manner by using 1,2,3-trichloropropene as thereactant in place of 2,3-dichloropropene.

To illustrate the antiozonant activity of the compounds of thisinvention, various rubber stocks are prepared. For all the rubber stocksdescribed as illustrative of the invention, Mooney scorch times at C.are determined by means of a Mooney Plastometer. The times in minutes (irequired for the Mooney reading to rise 5 points above the minimumviscosity is recorded. Longer times are indicative of greater processingsafety. The stocks are cured for the length of time required to obtainthe optimum cure. Curing characteristics are determined by means of theMonsanto Oscillating Disc Rheometer. From the Rheometer data the time tooptimum cure is determined and the stocks are cured in a press for thattime. The cure temperature is 144 C. in the case of natural rubberstocks; and 153 C. in the case of synthetic rubber stocks.

- Natural rubber stocks and their properties are shown in Table 1.

Zinc oxide 5.0 5.0 5.0 Stearic acid 3.0 3.0 3.0 Hydrocarbon softener 3.03.0 3.0 N-( Allyl )-N-'-phenylpphenylenediamine 1.5 N-( 2-Chloroal1yl)-N'-phenyl-pphenylenediamine 1.5 Mooney scorch times (t 13.0 6.8 11.6Modulus at 300% elongation 2550 2430 2460 Ultimate tensile strength 35003800 3800 Stock A is a control having no antidegradant, Stock B containsan antidegradant having no halo substitutents and Stock C contains acompound of this invention which has a halo substituent. It will benoted that Stock C has 70 percent more processing safety than Stock B.

Rubber ozone resistance data for the vulcanizates of Table 1 arerecorded in Table 11. The method used for measuring the ozone damage tovulcanized rubber is described by Decker and Wise, The Stress RelaxationMethod for Measuring Ozone Cracking," Rubber World, Apr. 1962, page 66.The test specimens are placed in an oven where a controlled atmosphereof ozone is maintained. in the static test, the test specimens are heldstationary under a given strain. In the dynamic test, the test specimensare flexed repeatedly to a 25 percent strain. The test specimens ofrubber are 2 inch long T-50 (ASTM D599-55) pieces died from standardstressstrain test sheets (ASTM D l 5-57T).

The stress-relaxation method is based on the principle that theeffective cross-sectional area of a small test piece of rubber isreduced by ozone cracking. The extent of cracking in a test piece isdetermined by measuring the forces required to extend the test piece 100percent before and after exposure to ozone. As the strip begins tocrack, the number of stresssupporting rubber chains decreases, and theforce required to extend the strip 100 percent is reduced. The ratio ofthis force to the original force is calculated at various intervals ofexpo sure to ozone. The graph of force vs. time is essentially astraight line, and the time required for attaining 90 percent, 80percent, and 70 percent of the original force is readily determined fromthe graph. The ability of the rubber to resist ozone attack is obtainedby comparison of these numbers. These ratios are the percent of originalmodulus of the rubber test piece and are listed as percent retention inthe table, infra. The ozone concentration for the tests is 25 partsozone per hundred million parts of air. Longer times in the datademonstrate better ozone resistance of the rubber stock.

TABLE 11 The data show that the vulcanizate containing the compound ofthis invention is more resistant to ozone degradation. The dynamic ozoneresistance data indicate that N-(2-chloroallyl)-N-phenyl-p-phenylene-diamine is about 75 percent betterthan N-(allyl)-N-phenyl-p-phenylenediamine for protecting rubber againstozone degradation when the rubber article is used under dynamicconditions.

Data for styrene-butadiene synthetic rubber stocks, their physicalproperties, and ozone resistance are shown in Table The data furtherdemonstrate that N-(2-ehloroallyl)-N'- phenyl-p-phenylenediamine hasgreater processing safety and improved ozone resistance.

Although the invention has been illustrated by typical examples, it isnot limited thereto. Changes and modifications of the examples of theinvention herein chosen for purposes of disclosure can be made which donot constitute departure from the spirit and scope ofthe invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A compound of the formula R1 /R2 @NKDNHCHM wherein R,, R and R arehydrogen or identical halogen, at least one being halogen.

2. A compound according to claim 1 wherein the halogen is chlorine.

3. A compound according to claim 2 wherein R and R are hydrogen.

2. A compound according to claim 1 wherein the halogen is chlorine.
 3. Acompound according to claim 2 wherein R2 and R3 are hydrogen.